Comparison of the Dislocation Structure of a CrMnN and a CrNi Austenite after Cyclic Deformation

Abstract

In the literature, the effects of nitrogen on the strength of austenitic stainless steels as well as on cold deformation are well documented. However, the effect of N on fatigue behaviour is still an open issue, especially when comparing the two alloying concepts for austenitic stainless steels-CrNi and CrMnN-where the microstructures show a different evolution during cyclic deformation. In the present investigation, a representative sample of each alloying concept has been tested in a resonant testing machine at ambient temperature and under stress control single step tests with a stress ratio of 0.05. The following comparative analysis of the microstructures showed a preferred formation of cellular dislocation substructures in the case of the CrNi alloy and distinct planar dislocation glide in the CrMnN steel, also called high nitrogen steel (HNS). The discussion of these findings deals with potential explanations for the dislocation glide mechanism, the role of N on this phenomenon, and the consequences on fatigue behaviour.

Physical Metallurgy of High Manganese Steels

“…This Special Issue gathers manuscripts from internationally recognized researchers with stimulating new ideas and original results. It consists of fifteen original research papers, seven contributions focus on steels with manganese content above 12% mass [4][5][6][7][8][9][10], whereas eight deal with alloys having less manganese [11][12][13][14][15][16][17][18].…”

“…The specific microstructural features that appear in HMnS during plastic deformation strongly influence their fatigue and fracture behaviour. Fluch et al [8] compared cold worked austenitic CrNi and CrMnN steels during cyclic loading. The higher strength of the CrMnN grade due to the high nitrogen content resulted in superior fatigue behaviour.…”